STRUCTURE OF THE HUMAN ALLELIC GLUTATHIONE-S-TRANSFERASE-PI GENE VARIANT, HGSTP1-ASTERISK-C, CLONED FROM A GLIOBLASTOMA-MULTIFORME CELL-LINE

We recently reported the cloning of full-length cDNAs corresponding to mRNAs of three GST-pi genes, hGSTP1A, hGSTP1*B and hGSTP1*C, as well as, the isolation of the full-length hGSTP1C, of the human glutathio ne S-transferase-pi (GST-pi) gene that is characterized by a A-->G tra nsition at + 1404 in exon 5 and a C --> T transition at + 2294 in exon 6. Although the promoter of the isolated gene was identical to that o f the previously described GST-pi gene isolated from the MCF 7 and the HPB-ALL cell lines, both of which were hGSTP1A, a number of structur al differences were observed, including, nucleotide transitions, trans versions, deletions and insertions, some of which created new restrict ion enzyme cleavage sites. A guanine insertion in the insulin response element, IRE, in intron 1 created an additional site for 5'-cytosine methylation. Seven repeat retinoic acid response element (RARE) consen sus half sites, A(G)GG(T)TC(G)A at + 1521 to + 1644 were identified in the cloned hGSTP1C. Five of the RARE half-sites had the minimal spac er nucleotide requirement for functionality and DNA mobility shift ana lysis with different pairs of the RARE half-sites and supershift studi es using antibodies against RAR-beta showed significant binding of nuc lear protein complexes from RA-treated cells to these RAREs. GST-pi ge ne expression was increased significantly in cells transfected with th e GST-pi gene and treated with all-trans RA. These results contrast wi th those in a previous report in which RA was shown to suppress the GS T-pi promoter, and indicate a complex mechanism of RA-mediated GST-pi gene regulation in tumor cells. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.